Koprivnikar Janet, Hoye Bethany J, Urichuk Theresa M Y, Johnson Pieter T J
Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada.
Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, USA.
Parasitol Res. 2019 Jan;118(1):275-288. doi: 10.1007/s00436-018-6154-6. Epub 2018 Nov 19.
In nature, multiple waves of exposure to the same parasite are likely, making it important to understand how initial exposure or infection affects subsequent host infections, including the underlying physiological pathways involved. We tested whether experimental exposure to trematodes (Echinostoma trivolvis or Ribeiroia ondatrae) affected the stress hormone corticosterone (known to influence immunocompetence) in larvae representing five anuran species. We also examined the leukocyte profiles of seven host species after single exposure to R. ondatrae (including four species at multiple time points) and determined if parasite success differed between individuals given one or two challenges. We found strong interspecific variation among anuran species in their corticosterone levels and leukocyte profiles, and fewer R. ondatrae established in tadpoles previously challenged, consistent with defense "priming." However, exposure to either trematode had only weak effects on our measured responses. Tadpoles exposed to E. trivolvis had decreased corticosterone levels relative to controls, whereas those exposed to R. ondatrae exhibited no change. Similarly, R. ondatrae exposure did not lead to appreciable changes in host leukocyte profiles, even after multiple challenges. Prior exposure thus influenced host susceptibility to trematodes, but was not obviously associated with shifts in leukocyte counts or corticosterone, in contrast to work with microparasites.
在自然界中，宿主很可能多次接触同一种寄生虫，因此了解初次接触或感染如何影响后续的宿主感染，包括其中涉及的潜在生理途径就显得尤为重要。我们测试了实验性暴露于吸虫（棘口吸虫或里氏并殖吸虫）是否会影响代表五种无尾两栖类物种的幼体中的应激激素皮质酮（已知其会影响免疫能力）。我们还检查了单次暴露于里氏并殖吸虫后的七个宿主物种的白细胞谱（包括四个物种在多个时间点的情况），并确定了接受一次或两次感染的个体之间寄生虫的感染成功率是否存在差异。我们发现，无尾两栖类物种之间在皮质酮水平和白细胞谱方面存在强烈的种间差异，并且先前受到感染的蝌蚪体内建立的里氏并殖吸虫数量较少，这与防御“预激发”一致。然而，暴露于任何一种吸虫对我们所测量的反应影响都很微弱。暴露于棘口吸虫的蝌蚪相对于对照组皮质酮水平降低，而暴露于里氏并殖吸虫的蝌蚪则没有变化。同样，即使经过多次感染，暴露于里氏并殖吸虫也不会导致宿主白细胞谱出现明显变化。因此，与微寄生虫的研究结果相比，先前的暴露会影响宿主对吸虫的易感性，但与白细胞计数或皮质酮的变化并无明显关联。
